jon153 wrote:
Somebody else posted on here that the K&N lets in more air, but the Mass Air Flow sensor compensates by increasing fuel to keep the air/ fuel ratio the same. You get more horsepower from the increased air/fuel mixture, but because you are using more fuel to get there your miles per gallon decreases. According to the theory, when you add more air, you have to add more fuel. Alternately, according to K&N, you get more horsepower and better gas mileage by letting more free flowing air in. They don't mention the air/fuel ratio in their literature but do claim better gas mileage.
I was just trying to find out if there was a reasonable chance of changing the fuel economy by changing the filter medium. It appears that there is but at what cost? A higher priced filter that has to be routinely cleaned and oiled versus a disposable paper one (that has to be replaced repeatedly)? The last time I cleaned the K&N it took most of one day and overnight to dry completely out.
K&N claims that the oil/ cotton filter traps dirt in the air allowing more "clean" air to get into the engine. They even state that as the filter gathers more dirt that the dirt trapping qualities are increased while the air flow remains unchanged.
I don't know but I was curious to see if this worked or not. It seems that a 1 mpg increase is not too bad.
Look at it this way, if you normally fill up at a 1/4 tank (@15 gallons) then increasing from 15 mpg to 16 mpg would theoretically be the equivalent of giving you approximately an extra gallon of gas free based on the increased distance you drove on the 15 gallons. (15 gallons x 15mpg= 225 miles while 15 gallons x 16mpg= 240 miles, a difference of 15 miles for the same amount of fuel). Not exact but you get my point.
As for the increased dirt, the engine oil (and oil filter) are supposed to also clean out contaminants in the engine so they should be routinely changed so that they can do their job effectively. Couple that with the lifetime power train warranty that came with the 2009's and I don't get too concerned with something failing. (I kept all of the paperwork and asked the mechanics at the dealership if the K&N would void the warranty- they said No).
So overall I would recommend a K&N but I am now very curious about the Amsoil filter (Thanks, Tommud!!!)
No MAF sensor on the 3.7.
With modern FI you can have upwards of a 80% clogged air filter with almost zero effects on mpg's or power if the rest of the engine(and powertrain) is in good working order.That is how effective OBDII systems are.
Now about more air flow is total BS.Alone more airflow at the intake will do nothing for performance or mpg's.Adding freeier flowing exhaust to that more intake air will do nothing to increase performance or mpg's(though may decrease them).Adding a custom PCM tune with both of those mods will do limited gains in performance and mpg's,and I mean limited gains.The only way to get big gains is all 3 added with upgraded engine internals that need and use those added aspects.Your engine is one big airpump,in stock form it can only pump so much air.Just adding a air filter that flows better will not increase how much air your engine pumps that is where longer duration cams and longer stroke,smaller combustion chambers come into play.
What poeple are seeing in increases by adding a fresh air tube to the stock box is that now the engine is sucking in considerably cooler air and it's fact that cooler air is denser(more O2) which does increase performance and mpg's with no internal engine mods since it's pumping the same amount of air,so same fuel/air mixture but more O2 means more power.
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